coresight: trbe: Add infrastructure for Errata handling

Add a minimal infrastructure to keep track of the errata
affecting the given TRBE instance. Given that we have
heterogeneous CPUs, we have to manage the list per-TRBE
instance to be able to apply the work around as needed.
Thus we will need to check if individual CPUs are affected
by the erratum.

We rely on the arm64 errata framework for the actual
description and the discovery of a given erratum, to
keep the Erratum work around at a central place and
benefit from the code and the advertisement from the
kernel. Though we could reuse the "this_cpu_has_cap()"
to apply an erratum work around, it is a bit of a heavy
operation, as it must go through the "erratum" detection
check on the CPU every time it is called (e.g, scanning
through a table of affected MIDRs). Since we need
to do this check for every session, may be multiple
times (depending on the wrok around), we could save
the cycles by caching the affected errata per-CPU
instance in the per-CPU struct trbe_cpudata.

Since we are only interested in the errata affecting
the TRBE driver, we only need to track a very few of them
per-CPU.  Thus we use a local mapping of the CPUCAP for the
erratum to avoid bloating up a bitmap for trbe_cpudata.

i.e, each arm64 TRBE erratum bit is assigned a "index"
within the driver to track. Each trbe instance updates
the list of affected erratum at probe time on the CPU.
This makes sure that we can easily access the list of
errata on a given TRBE instance without much overhead.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20211019163153.3692640-10-suzuki.poulose@arm.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>